The long-term goal of our investigation is to understand the function of basophils and mast cells in immunologic reactions of both immediate and delayed-type hypersensitivity, in neoplasia and in normal physiology. Recent progress to this end has been to describe anaphylactic degranulation and recovery and uropod formation in guinea pig basophils and in human basophils. We also identified certain cloned mouse cells as mast cells and described their sodium butyrate-induced maturation and glycosaminoglycan content. This was accompanied by the first ultrastructural description of mouse basophils and their simularities to cloned mouse NK cells expressing high affinity IgE receptors and to cloned, granulated mouse suppressor lymphocytes. Unpublished studies include detailed analysis of purified human lung mast cell degranulation, a large number of basophil-like granulated mouse clones, from several laboratories, which express NK or CTL function and degranulation and recovery of cloned mouse mast cells.